Measurement of the ¹⁴⁵Sm half-life

The half-life of ¹⁴⁵Sm has been measured by means of the reference source method with a HPGe detector. The long-lived radionuclide ⁴⁴Ti was mixed into the source for reference. The time-dependency of the ¹⁴⁵Sm/⁴⁴Ti activity ratio was followed by assessing the count-rate ratio of their characteristic gamma-ray emissions at 61.2 keV (¹⁴⁵Sm) and 67.9/78.3 keV (⁴⁴Ti) in spectra recorded over periods of typically one day. In total, 220 measurements were performed over a period of 384 days or about one half-life period. The experiment and ensuing uncertainty budget are discussed in detail. Different error propagation is applied for random uncertainties, autocorrelated structures in the fit residuals, and potential systematic errors. The result for the ¹⁴⁵Sm half-life, 345 (16) d, is compatible with the scarce literature values, however the experimental details of the old measurements were barely documented.